The invention relates to a method for securing a motor vehicle against theft. The invention furthermore relates to a system for securing a motor vehicle against theft through means for switching over at least one essential operational element of the motor vehicle, the means for switching comprising at least one usage authorization device, at least one switching device switching between specific operational states of the essential operational element(s) and means for transmitting the authorization data between the usage authorization device and the switching device.
In the majority of current automobiles immobilizers are already installed, such as have been described for example in GB 2279479 A, DE 9414476 and DE 19604206. However, this type of immobilizer can already be circumvented for example thereby that the unauthorized person receives the coded signal of a transponder which discloses the identity of the authorized person, and can subsequently identify himself accordingly. Such an immobilizer of the vehicle is therefore readily circumvented.
A further security problem is the so-called “car napping”, in which the authorized person together with the motor vehicle is forced to make it possible for the unauthorized person to use the vehicle.
DE 4440975 has already dealt with this problem. This document proposes a protection device against third party use for motor vehicles with a usage control device, in which a transmitting device external to the vehicle continuously transmits periodically successive vehicle-specific usage signals to the usage control device in order to permit the use of the vehicle.
However, this type of securement has significant disadvantages. For example the involvement of an additional certification site, such as for example the police or the motor vehicle manufacturer, is necessary in order to make possible the secure operation of the system. This also causes additional expenses.
The system is furthermore limited with respect to the particular usage times and the particular usage area and these cannot be set arbitrarily and are therefore inflexible.
Furthermore, it is possible in the case of this third party usage protection device to obtain from the authorized person the usage control device, for example a mobile telephone, by force through car napping and thereby to circumvent the system at least for a time.